JiEAKED IV HALES 221 



Mesoplodon kaasti, Flower.* Rostrum narrow at 

 base ; basirostral grooves present ; foramina of fifth 

 nerve one behind the other. Tooth very large, near 

 middle of jaw. 



This species is only known from a rostrum and a 

 mandible. But the peculiar form (triangular with 

 a conical point) and large size of teeth seem to mark 

 it out. 



Finally, there is the species Mesoplodon stejnegeri, 

 of True,f which has an unusually large brain case 

 (half the length of the skull) ; no basirostral grooves, 

 and the two foramina one behind the other. This 

 skull, which came from Behring Straits, has no lower 

 jaw. 



The genus HYPEROODON may be distinguished by 

 the following features : Skull with enormous maxil- 

 lary crests (in adult males). Mesethmoid not fully 

 ossified. A single tooth on each ramus of lower 



O 



jaw ; also numerous small teeth as Ziphius. Verte- 

 bral formula: C. 7; D. 9; L. 9; Ca. 18 = 43. 

 Cervicals fused into one mass, the last sometimes 

 free. Sternum consisting of three pieces, the last 

 of which is bifid posteriorly. 



In more than one feature Hyperoodon, of all 

 Ziphioids, comes nearest to Physetcr. The great 



* Trans. Zool. Soc., x., p. 421. In a recent memoir upon Mesoplodon 

 (Proc. Zool. Soc., 1893, p. 216) Mr. H. O. Forbes seeks to unite with 

 M. grayi, Haast, Sir W. Flower's species, M. australis and M. haasti. 



t "Description of a New Species of Mesoplodon" etc., Proc. U. S. 

 Nat. Mus., 1885, p. 584. 



